linux-kernel - Re: [PATCH] staging: kpc2000: Use memset to initialize resources

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Message-ID: <CAKwvOdkRc8o+g=crw2xCesWR53bnYTtx2BXuxEbR_Hec5UNuGQ@mail.gmail.com>
Date:   Wed, 24 Apr 2019 15:44:50 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devel@...verdev.osuosl.org, LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] staging: kpc2000: Use memset to initialize resources

On Wed, Apr 24, 2019 at 11:58 AM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> Clang warns:
>
> drivers/staging/kpc2000/kpc2000/cell_probe.c:96:38: warning: suggest
> braces around initialization of subobject [-Wmissing-braces]
>     struct resource  resources[2] = {0};
>                                      ^
>                                      {}
> drivers/staging/kpc2000/kpc2000/cell_probe.c:314:38: warning: suggest
> braces around initialization of subobject [-Wmissing-braces]
>     struct resource  resources[2] = {0};
>                                      ^
>                                      {}
> 2 warnings generated.
>
> One way to fix these warnings is to add additional braces like Clang
> suggests; however, there has been a bit of push back from some
> maintainers, who just prefer memset as it is unambiguous, doesn't
> depend on a particular compiler version, and properly initializes all
> subobjects [1][2]. Do that here so there are no more warnings.
>
> [1]: https://lore.kernel.org/lkml/022e41c0-8465-dc7a-a45c-64187ecd9684@amd.com/
> [2]: https://lore.kernel.org/lkml/20181128.215241.702406654469517539.davem@davemloft.net/
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/455
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>  drivers/staging/kpc2000/kpc2000/cell_probe.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/staging/kpc2000/kpc2000/cell_probe.c b/drivers/staging/kpc2000/kpc2000/cell_probe.c
> index ad2cc0a3bfa1..13f544f3c0b9 100644
> --- a/drivers/staging/kpc2000/kpc2000/cell_probe.c
> +++ b/drivers/staging/kpc2000/kpc2000/cell_probe.c
> @@ -93,8 +93,8 @@ void parse_core_table_entry(struct core_table_entry *cte, const u64 read_val, co
>  int  probe_core_basic(unsigned int core_num, struct kp2000_device *pcard, char *name, const struct core_table_entry cte)
>  {
>      struct mfd_cell  cell = {0};
> -    struct resource  resources[2] = {0};
> -
> +    struct resource  resources[2];
> +
>      struct kpc_core_device_platdata  core_pdata = {
>          .card_id           = pcard->card_id,
>          .build_version     = pcard->build_version,
> @@ -112,6 +112,8 @@ int  probe_core_basic(unsigned int core_num, struct kp2000_device *pcard, char *
>      cell.id = core_num;
>      cell.num_resources = 2;
>
> +    memset(&resources, 0, sizeof(resources));
> +
>      resources[0].start = cte.offset;
>      resources[0].end   = cte.offset + (cte.length - 1);
>      resources[0].flags = IORESOURCE_MEM;
> @@ -311,8 +313,8 @@ int  probe_core_uio(unsigned int core_num, struct kp2000_device *pcard, char *na
>  static int  create_dma_engine_core(struct kp2000_device *pcard, size_t engine_regs_offset, int engine_num, int irq_num)
>  {
>      struct mfd_cell  cell = {0};
> -    struct resource  resources[2] = {0};
> -
> +    struct resource  resources[2];
> +
>      dev_dbg(&pcard->pdev->dev, "create_dma_core(pcard = [%p], engine_regs_offset = %zx, engine_num = %d)\n", pcard, engine_regs_offset, engine_num);
>
>      cell.platform_data = NULL;
> @@ -321,6 +323,8 @@ static int  create_dma_engine_core(struct kp2000_device *pcard, size_t engine_re
>      cell.name = KP_DRIVER_NAME_DMA_CONTROLLER;
>      cell.num_resources = 2;
>
> +    memset(&resources, 0, sizeof(resources));
> +

Bonus points for clearing up the leading whitespace.  Thanks for the
patch.  I'm beginning to think aggregate initializers are the devil.
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>      resources[0].start = engine_regs_offset;
>      resources[0].end   = engine_regs_offset + (KPC_DMA_ENGINE_SIZE - 1);
>      resources[0].flags = IORESOURCE_MEM;
> --
> 2.21.0
>


-- 
Thanks,
~Nick Desaulniers